The present invention relates in general to an apparatus and a method for inspecting a screen of a displaying device, and more particularly, an apparatus and a method for inspecting a screen of a displaying device, wherein an image frame synchronizing signal can be synchronized at a random phase point of a pattern frame synchronizing signal.
An image inspection apparatus is used to inspect the quality of an image such as contrast, convergence, focus, etc. of an image displaying apparatus such as a cathode-ray tube (CRT), in the final stage of the production process of the displaying apparatus.
The conventional image inspection apparatus is, as shown in FIG. 4, comprised of a pattern generator 111 connected to a CRT 101 to be inspected, a camera 121 installed in front of the CRT 101, and an image inspector 131 connected to the camera 121. The pattern generator 111 is comprised of a pattern signal generating part 113 generating an inspection pattern signal for an inspection pattern such as a cross-hatch pattern to be displayed on the CRT 101, and a pattern synchronizing signal generating part 115 generating a pattern frame synchronizing signal as a trigger signal to display the inspection pattern periodically on the CRT. The camera 121 is comprised of a grabbing part 122 grabbing the inspection pattern displayed on the CRT 101, and an image frame synchronizing signal generating part 126 generating an image frame synchronizing signal as a trigger signal allowing the grabbing part 122 to periodically grab the inspection pattern displayed on the CRT 101. The image inspector 131 is comprised of an image processing part 113 converting an analog image signal of the inspection pattern from the camera 121 into a digital image signal, and a memory 135 storing the converted digital image signal therein.
Hereinbelow, an image inspection method using the conventional image inspection apparatus will be described.
First, the pattern generator 111 generates the inspection pattern signal and a pattern synchronizing signal. The pattern synchronizing signal is comprised of the pattern frame synchronizing signal and a pattern horizontal synchronizing signal; the pattern frame synchronizing signal divides the inspection pattern displayed on the CRT 101 frame by frame, and the pattern horizontal synchronizing signal divides the inspection pattern within a frame in lines. The frequency of the pattern frame synchronizing signal varies depending upon the image displaying apparatus. For example, the image displaying apparatus according to the National Television System Committee (NTSC) system has the frequency of the pattern frame synchronizing signal of 60 Hz whereas CRT monitors and digital TVs have the frequency of the pattern frame synchronizing signal more than 60 Hz. The inspection pattern is continuously displayed on the CRT 101 according to the pattern synchronizing signal. The inspection pattern displayed on the CRT 101 is grabbed by the camera 121 according to the image frame synchronizing signal. The frequency of the image frame synchronizing signal is 60 Hz in the case of the camera employing the NTSC system, but which may vary depending upon the type of the camera 121. The inspection pattern displayed on the CRT varies in position and brightness, etc. in response to adjustment of focus and convergence, etc. of the CRT 101, and therefore, it is necessary to continuously grab the inspection pattern displayed on the CRT 101 during adjustment. The analog image signal of the inspection pattern grabbed by the grabbing part 122 is inputted into the image inspector 131. The inputted analog image signal is converted into a digital image signal by the image processing part 133, and the converted image signal is stored in the memory 135. The image of the CRT 101 is inspected by obtaining a brightness value of the inspection pattern from the digital image signal.
However, according to the conventional image inspection apparatus, where the pattern frame synchronizing signal and the image frame synchronizing signal have different frequencies, a phenomenon that a bright or dark part of the grabbed image flows vertically is generated on the image of the inspection pattern grabbed by the camera 121. Further, as shown in FIG. 5, the phase difference between the continuous pattern frame synchronizing signals (A) and the image frame synchronizing signals (B and C) varies whenever the inspection pattern is grabbed. In FIG. 5, a zero phase point of the pattern frame synchronizing signal (A) is denoted D, the frequency of the pattern frame synchronizing signal (A) is 80 Hz, and the frequencies of the image frame synchronizing signals (B and C) are both 60 Hz. Therefore, the noise interfered whenever an image of the inspection pattern is grabbed is not standardized, thereby lowering the reliability of the image inspection. A further problem has occurred in inspecting an image of 60 Hz as a high definition monitor whose vertical frequencies have sharply increased has recently released in the market. The same problem is expected in the case of color TV sets having an improved high definition.
Accordingly, the present invention has been made keeping in mind the above-described shortcomings, and it is an object of the present invention to provide an apparatus and a method for inspecting an image, synchronizing a pattern frame synchronizing signal and an image frame synchronizing signal to initiate grabbing an inspection pattern, where the pattern frame synchronizing signal and the image frame synchronizing signal have different frequencies.
This and other objects of the present invention may be achieved by a provision of an apparatus for inspecting an image of an image displaying apparatus, comprising a pattern generator provided with a pattern signal generating part generating an inspection pattern signal and a pattern frame synchronizing signal generating part generating a pattern frame synchronizing signal and displaying an inspection pattern on the image displaying apparatus according to the inspection pattern signal and pattern frame synchronizing signal; a camera provided with an image frame synchronizing signal generating part generating an image frame synchronizing signal, grabbing the inspection pattern displayed on the image displaying apparatus according to the image frame synchronizing signal; a phase selecting part selecting a random phase point of the pattern frame synchronizing signal generated by the pattern frame synchronizing signal generating part; and a V-sync signal synchronizing part synchronizing a first signal among the image frame synchronizing signals generated by the image frame synchronizing signal generating part with the phase point selected in the phase selecting part.
Preferably, the phase point is a zero phase point of the pattern frame synchronizing signal.
The pattern frame synchronizing signal generating part generates a plurality of pattern frame synchronizing signals having different frequencies, said apparatus further comprising a signal selection part selecting a pattern frame synchronizing signal among the plurality of pattern frame synchronizing signals generated by the pattern frame synchronizing signal generating part; and a control part controlling the pattern frame synchronizing signal generating part so as to generate the pattern frame synchronizing signal selected by the signal selection part.
According to another aspect of the present invention, this and other objects may also be achieved by a method for inspecting an image of an image displaying apparatus, comprising the steps of generating an inspection pattern signal and a pattern frame synchronizing signal; displaying an inspection pattern on the image displaying apparatus according to the inspection pattern signal and pattern frame synchronizing signal; selecting a random phase point of the pattern frame synchronizing signal; generating an image frame synchronizing signal to allow a first signal of the image frame synchronizing signals to be synchronized with the phase point selected at the phase point selecting step; and grabbing the inspection pattern displayed on the image displaying apparatus according to the image frame synchronizing signal.
Preferably, the phase point is a zero phase point of the pattern frame synchronizing signal.
The step of generating the pattern frame synchronizing signal is comprised of the substeps of generating a plurality of pattern frame synchronizing signals having different frequencies; selecting one among the plurality of pattern frame synchronizing signals; and generating the selected pattern frame synchronizing signal.